According to Continente Multicultural magazine, "Spanish Bombs" is a pop rock song.[3]AllMusic's Donald A. Guarisco described it as a "rousing rocker" with a combination of power chords, quickly-strummed acoustic riffs, and "simple but catchy verses and chorus".[4]

"Spanish Bombs" compares the modern day tourist experience of Spain with the circumstances of the Spanish Civil War,[2] and contrasts the "trenches full of poets" to the planeloads of British tourists visiting the country's beaches in the post-Franco era.[5] Praising the heroism of the civil war republicans,[6] the song alludes to the death of anti-fascist poet Federico Garcia Lorca.[7] Adrien Begrand of PopMatters remarked that Strummer's references to bomb attacks by Basque separatists in the late 1970s "echoes" Lorca and the Spanish Civil War, citing the line "Spanish bombs rock the province / I'm hearing music from another time".[8]

The song utilizes what Adam Mazmanian of The Washington Times calls "pidgin Spanish".[5] According to the liner notes accompanying the original 1979 UK vinyl release of London Calling the song included the lyric "Yo t'quierro y finito, yo te querda, oh ma côrazon" (sic).[9] According to The A.V. Club, the lyric is, in fact, "Yo te quiera infinito, yo te quiera, oh mi corazón" which translates as "I want you forever, I want you, oh my heart".[10] The song also makes reference to Andalucia, the Spanish region where Strummer's ex-girlfriend Palmolive was born.[2]